Many surface ships utilize marine boilers for propulsion. These boilers include steam and mud drums with manhole access hatches. During boiler inspection and/or repair these manhole hatches are opened to permit personnel to enter the drums. In order to enter through the manhole access a cover inside the drum is removed. This cover must be replaced after the work is accomplished. Manhole accesses are characteristically elliptical in shape and have an elliptical sealing surface in the interior of the drum for making the required seal with the cover. This interior elliptical sealing surface is subjected to extreme corrosive forces of steam in the steam drum and mineralized water in the mud drum. Consequently once the seal is broken by removing the cover the heavily corroded surface must be repaired to a smooth, flat machined finish so that the cover will adequately reseal the steam or mud drum. Submarines also have tanks with a boiler type manhole access hatch which are frequently opened for inspection and/or repair. These sealing surfaces, which are also elliptical, are subjected to extreme corrosion. These sealing surfaces must also be repaired to a smooth machined finish prior to closure of the tank.
The present practice of refurbishing elliptical sealing surfaces of manhole access hatches is to clad weld the surface to provide a material buildup therealong and then grind the surface smooth with a hand grinding machine. The buildup may also be accomplished by metal electroplating. Both of these methods are very time consuming and fall far short of restoring the sealing surface to the original machined surface. In some instances the access hatch is removed from the steam or mud drum or submarine tank by oxygen cutting so that the hatch can be sent to a machine shop for machining the sealing surface. Replacement of the access hatch involves critical rewelding which must pass very rigid inspection requirements. This whole process is very expensive and time consuming.